a nursing care plan is the determination of the patient's nursing problems. diagnosis of those nursing problems is based on the assessment you make. assessment includes information you gather from:

a health history (review of systems) [font=arial unicode ms]

performing a physical exam - what you listed was heartburn (when does this occur and how often? what foods cause it?), dyspepsia (this is the same as heartburn), chest pain (where, when, how long does it last, what brings it on, what relieves it), regurgitation

reviewing the pathophysiology, signs and symptoms and complications of their medical condition - you need to look up the pathophysiology of gerd to understand what is going on with this condition and why the symptoms occur.

definition of imbalanced nutrition: less than body requirements: intake of nutrients insufficient to meet metabolic needs

the problem with diagnosing this is that you presented no data that the patient is eating less than their metabolic need. you have no data that they have lost weight, a calorie count to indicate that they are eating less than their daily required need or evidence of anorexia.

chronic chest pain related to ineffective digestion.

definition of chronic pain: unpleasant sensory or emotional experience arising from actual or potential tissue damage or described in terms of such damage

ineffective digestion is not going to be the cause of any actual or potential tissue damage with gerd. this is why you need to read about the disease and understand the pathophysiology going on in order to word the related factor for this diagnosis correctly.